Pumps are known for the simultaneous discharge of a liquid from a reservoir bottle and air from the atmosphere. One example of such a pump is U.S. Pat. No. 5,271,530 to Uehira et al, issued Dec. 21, 1993. The inventors of the present invention have appreciated that such previously known pumps suffer the disadvantages that they are formed from a large number of parts, and are complex in their manufacture of the different parts leading to increased costs for manufacture and assembly.
The present inventors have appreciated that pumps are known which use diaphragm members, however, it is appreciated that disadvantages arise in respect of the construction of known diaphragm members so as to facilitate their manufacture and advantageous sealing engagement with other elements of the pumps.